An internal combustion engine of a vehicle may be provided with a variable valve gear including a cam follower oscillated by a drive cam and an oscillating cam oscillated by the cam follower to open and close a valve, the variable valve gear opening and closing the valve by oscillating the oscillating cam using a drive force transmitted from the cam follower to the oscillating cam while changing the lift characteristics of the valve using the drive force transmitted to the oscillating cam.
A variable valve gear disclosed in Japanese Patent No. 4362249 is provided with a second interposing arm (cam follower) oscillated by a rotary cam (drive cam) of a camshaft (drive camshaft) and a first interposing arm (oscillating cam) oscillated by the second interposing arm, the variable valve gear opening and closing a valve by the oscillation of the first interposing arm and changing an oscillation amount of the first interposing arm by changing an arm ratio of the second interposing arm.
A variable valve gear disclosed in Japanese Patent No. 4026634 is provided with a control shaft in parallel with a camshaft having a drive cam, an oscillating member (oscillating cam) on the control shaft, an intermediate member (cam follower) in contact with the drive cam between the drive cam and the oscillating member, a control member rotatable on the camshaft, a support member on the control member, and a rotary interlocking mechanism for interlocking the rotation of the control member to the control shaft, the variable valve gear changing a rotary angle of the control shaft and changing a position of the intermediate member on a surface of the drive cam and a position thereof on a surface of a slide.
In the conventional variable valve gears disclosed in Japanese Patent No. 4362249 and Japanese Patent No. 4026634, a rocker arm or an oscillating cam has a contact surface where the rocker arm and the oscillating cam are in contact with a roller of which a relative position is changed with respect to the rocker arm and the oscillating cam. Therefore, in order to ensure the contact surface of the roller, a long rocker arm is necessary in Japanese Patent No. 4362249 and a long oscillating cam is necessary in Japanese Patent No. 4026634. Consequently, a device is disadvantageously enlarged and mountability in an internal combustion engine is impaired.
As shown in FIG. 10, in the conventional variable valve gears, the maximum lift position of a valve is approximately constant (as shown by dashed line P) and therefore, it is difficult to adjust a valve timing in accordance with a lift state of the valve. Thus, the pumping loss and the fuel consumption are disadvantageously increased.